The invention relates to a motor chain saw comprising a drive motor driving by means of a sprocket wheel a saw chain, wherein teeth of the sprocket wheel engage the saw chain and the saw chain is supplied with chain oil for lubrication by means of a supply pump. The supply pump is driven by a pump drive that is comprised of a first drive wheel connected with the supply pump and a second drive wheel that is connected with the sprocket wheel, wherein the drive wheels are drivingly connected to each other. The second drive wheel is formed on a drive element provided with a coupling section that produces a positive fit drive connection between the drive element and the sprocket wheel, for which purpose the coupling section has followers having correlated therewith follower surfaces formed on the sprocket wheel, wherein in circumferential direction of the sprocket wheel several follower surfaces of the sprocket wheel are contacting several followers of the coupling section.
U.S. Pat. No. 6,523,645 B1 discloses a supply pump of a motor chain saw by means of which chain oil is supplied to a saw chain that is driven by means of a sprocket wheel. The pump drive of the supply pump is comprised of a first drive wheel that is connected to the supply pump and a second drive wheel that is connected to the sprocket wheel; the drive wheels are in driving connection with each other. The second drive wheel is embodied as a worm gear on a drive element that engages with a coupling section the sprocket wheel such that it is in positive fit drive connection with the sprocket wheel. The coupling section has for this purpose several followers distributed about the circumference and the followers have correlated therewith follower surfaces that are formed on the sprocket wheel. In this context, the followers each engage between two teeth of the driving sprocket wheel and are in drive connection with the sprocket wheel.
When a motor chain saw is to be furnished with a different saw chain, for example, provided with a different pitch, the sprocket wheel must be exchanged in accordance with the type of the employed saw chain in order to ensure a drive connection with the sprocket wheel that matches shape and pitch of the saw chain. When the geometry of the sprocket wheel is changed, the drive element for the supply pump must be changed also because the coupling section is configured in accordance with the geometry of the employed sprocket wheel.
Upon exchange of a saw chain kit, not only the sprocket wheel but also the drive element for the supply pump must therefore be exchanged; this is a complex process and cumbersome.